全文获取类型
收费全文 | 851篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 160篇 |
金属工艺 | 17篇 |
机械仪表 | 11篇 |
建筑科学 | 39篇 |
能源动力 | 16篇 |
轻工业 | 43篇 |
水利工程 | 5篇 |
无线电 | 47篇 |
一般工业技术 | 120篇 |
冶金工业 | 308篇 |
原子能技术 | 5篇 |
自动化技术 | 91篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 41篇 |
2012年 | 23篇 |
2011年 | 49篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 27篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1990年 | 8篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1972年 | 9篇 |
1970年 | 9篇 |
1955年 | 8篇 |
排序方式: 共有877条查询结果,搜索用时 15 毫秒
61.
Jerome BlairAuthor Vitae 《Computer Standards & Interfaces》2011,33(2):122-127
The Peano Kernel Theorem is introduced and a frequency domain derivation is given. It is demonstrated that the application of this theorem yields simple and accurate formulas for estimating the error introduced into a signal by filtering it to reduce noise. The concept of the order of accuracy of a filter is introduced and used as an organizing principle to compare the accuracy of different filters. 相似文献
62.
William T. Riley Steven C. Carson Norman Martin Albert Behar Valerie L. Forman-Hoffman Albert Jerome 《Computers in human behavior》2005,21(6):1005-1018
This study sought to evaluate the feasibility of a researcher configurable self-monitoring program. An initial prototype of the program was developed as a Windows-based drag and drop flow chart interface for the researcher to construct the self-monitoring or diary protocol to be scheduled and displayed to the subject on a Pocket PC. The usability of the desktop researcher interface was evaluated in a small sample of medication trial researchers whose ratings of the prototype were generally positive and provided directions for improvement. The subject interface was then evaluated in an “analog” drug trial of 49 smokers using nicotine gum. These subjects were randomly assigned to either paper-based log or Pocket PC self-monitoring for 3 weeks. Pocket PC subjects were significantly more compliant than the log subjects on recording in the second (65% vs. 39%) and third (69% vs. 39%) weeks of the trial but did not differ from the log condition on total recording entries, likely due to the restrictions on retrospective recording in the Pocket PC program. This study provides support for the feasibility of a researcher configurable electronic diary system which should substantially reduce the programming barriers to electronic self-monitoring and increase the use of real-time monitoring in clinical and research venues. 相似文献
63.
Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag-0.6Cu solder 总被引:4,自引:0,他引:4
Long-term, solid-state intermetallic compound (IMC) layer growth was examined in 95.5Sn-3.9Ag-0.6Cu (wt.%)/copper (Cu) couples.
Aging temperatures and times ranged from 70°C to 205°C and from 1 day to 400 days, respectively. The IMC layer thicknesses
and compositions were compared to those investigated in 96.5Sn-3.5Ag/Cu, 95.5Sn-0.5Ag-4.0Cu/Cu, and 100Sn/Cu couples. The
nominal Cu3Sn and Cu6Sn5 stoichiometries were observed. The Cu3Sn layer accounted for 0.4–0.6 of the total IMC layer thickness. The 95.5Sn-3.9Ag-0.6Cu/Cu couples exhibited porosity development
at the Cu3Sn/Cu interface and in the Cu3Sn layer as well as localized “plumes” of accelerated Cu3Sn growth into the Cu substrate when aged at 205°C and t>150 days. An excess of 3–5at.%Cu in the near-interface solder field
likely contributed to IMC layer growth. The growth kinetics of the IMC layer in 95.5Sn-3.9Ag-0.6Cu/Cu couples were described
by the equation x=xo+Atnexp [−ΔH/RT]. The time exponents, n, were 0.56±0.06, 0.54±0.07, and 0.58±0.07 for the Cu3Sn layer, the Cu6Sn5, and the total layer, respectively, indicating a diffusion-based mechanism. The apparent-activation energies (ΔH) were Cu3Sn layer: 50±6 kJ/mol; Cu6Sn5 layer: 44±4 kJ/mol; and total layer: 50±4 kJ/mol, which suggested a fast-diffusion path along grain boundaries. The kinetics
of Cu3Sn growth were sensitive to the Pb-free solder composition while those of Cu6Sn5 layer growth were not so. 相似文献
64.
Golden hamsters (Mesocricetus auratus) and dwarf hamsters (Phodopus campbelli) interacted with a conspecific demonstrator that had recently consumed a flavored food. When given a choice between their demonstrator's flavor and another flavor, the dwarf hamsters preferred the flavor their demonstrator had eaten. Golden hamsters did not prefer their demonstrators' diets when the demonstrators were unrelated adults or littermates, but they did when the demonstrator was their mother. Videotaping the interactions between demonstrators and observers revealed that adult golden hamsters did not investigate foods hoarded by their demonstrators whereas dwarf hamsters did. These results are interpreted in terms of the stimuli that activate feeding behavior systems in these 2 hamster species. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
Tetramethylammonium 3-aminopropyl dimethylsilanolate, readily prepared from bis(3-aminopropyl) tetramethyldisiloxane and tetramethyl-ammonium hydroxide pentahydrate, has been found to serve as a highly effective catalyst for the ring opening polymerization of cyclic siloxanes with an end blocker such as bis(3-aminopropyl) tetramethyldisiloxane to give aminopropyl terminated linear polydimethylsiloxanes. By following a novel two stage procedure, even high molecular weight (5,000–55,000 g/mol) silicone diamines were able to be prepared in a high state of purity; chain extension reactions of these diamines with diisocyanates gave a series of high molecular weight silicone polyureas with good elastomeric properties. 相似文献
66.
Jerome L. Hojnacki Joanne E. Cluette-Brown Randall N. Deschenes John J. Mulligan Thaddeus V. Osmolski Nicholas J. Rencricca Joseph J. Barboriak Joseph A. Jakubowski 《Lipids》1991,26(11):884-890
The present study was designed to investigate the effect of ethanol (EtOH) dose on low density lipoprotein (LDL) and platelet
composition. Male squirrel monkeys were divided into three groups designated Control, Low, and High EtOH, and fed isocaloric
liquid diets containing 0%, 12%, and 24% of calories as EtOH, respectively. After four months of treatment, monkeys fed the
12% alcohol dose had LDL and platelet cholesterol concentrations similar to Controls. By contrast, platelet membranes from
High EtOH animals contained significantly more cholesterol which was associated with higher levels of plasma LDL cholesterol
and apolipoprotein B. Blood platelet count, size, and mass were similar for all groups and circulating platelet aggregates
were absent in the two alcohol cohorts. Despite elevations in platelet cholesterol mass and thromboxane A2 (TXA2) precursor, phospholipid arachidonate, platelet responsiveness, measured as thromboxane formed in response to a collagen
challengein vitro, and the cholesterol/phospholipid molar ration, were not significantly altered by high dose alcohol. Normal platelet activity
in High EtOH monkeys may have resulted from a significant increase in the platelet phospholipid polyunsaturated/saturated
fatty acid ratio and a non-significant increase in platelet phospholipid mass, both of which would have a fluidizing effect
on platelet membranes. Our data indicate that low EtOH intake has no effect on platelet composition and function while unfavorable
platelet cholesterol enrichment following consumption of high dose ethanol may arise from elevations in plasma LDL. Potentially
thrombogenic (TXA2 formation, platelet aggregate formation) consequences of increased platelet cholesterol in squirrel monkeys fed high levels
of alcohol may be averted by compensatory physicochemical changes in platelet membrane lipid composition although persistent
elevations in circulating LDL may contribute to increased risk of cardiovascular disease. 相似文献
67.
An adaptive approach to human decision making: Learning theory, decision theory, and human performance. 总被引:1,自引:0,他引:1
Describes a general model of decision rule learning, the rule competition model, composed of 2 parts: an adaptive network model that describes how individuals learn to predict the payoffs produced by applying each decision rule for any given situation and a hill-climbing model that describes how individuals learn to fine tune each rule by adjusting its parameters. The model was tested and compared with other models in 3 experiments on probabilistic categorization. The 1st experiment was designed to test the adaptive network model using a probability learning task, the 2nd was designed to test the parameter search process using a criterion learning task, and the 3rd was designed to test both parts of the model simultaneously by using a task that required learning both category and cutoff criteria. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
Repeated measures designs involving nonorthogonal variables are being used with increasing frequency in cognitive psychology. Researchers usually analyze the data from such designs inappropriately, probably because the designs are not discussed in standard textbooks on regression. Two commonly used approaches to analyzing repeated measures designs are considered in this article. It is argued that both approaches use inappropriate error terms for testing the effects of independent variables. A more appropriate analysis is presented, and two alternative computational procedures for the analysis are illustrated. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
José F. Bartolomé Isabel Montero Marcos Díaz Sonia López-Esteban José S. Moya Sylvain Deville Laurent Gremillard Jerome Chevalier Gilbert Fantozzi 《Journal of the American Ceramic Society》2004,87(12):2282-2285
The aging behavior of 3-mol%-yttria-stabilized tetragonal zirconia (3Y-TZP) ceramics sintered in air and in reducing conditions was investigated at 140°C in water vapor. It was observed by X-ray diffraction (XRD) that 3Y-TZP samples sintered in reducing conditions exhibited significantly higher tetragonal-to-monoclinic transformation than samples with similar density and average grain size values but obtained by sintering in air. This fact is explained by the increase of the oxygen vacancy concentration and by the presence at the grain boundary region of a new aggregate phase formed because of the exolution of Fe2+ ions observed by X-ray photoelectron spectroscopy. 相似文献
70.